Gas-filled tube



my 13, 1930- w. F. HENDRY GAS FILLED TUBE Filed Dec. 11 1926 Patented May 13,1930

UNITD oFFIcE? WILLIAM F. HENDRY, 01E OSSIN'ING, NEW YORK, ASSIGNOR TO MANHATTAN ELEC- TRICAL SUPPLY COMPANY, INGI, A CORPORATION OF MASSACHUSETTS GAS-FILLED TUBE This invention relates to gas-filled tube signs, and more particularly to blue colored gaseous tubes.

In order to obtain a blue colored tubesign 5 it has been the practice to introduce mercury into a neon-filled glass or other transparent or translucent envelope and, by means of internal electrodes, create an electrical discharge which will ionize the gaseous content of the tube. The mercury is vaporized at high temperatures created by a high tension discharge, and this will give the tube its characteristic blue color. If such sign tubes are subjectedtotemperature changes, then the running temperature of the tube has to be high enough to prevent solidification of the mercury at the minimum temperature prevailing in the place, because otherwise an advertising sign which is blue at noon may turn orange (the color of ionized neon) in the evening. Tubes Which are operated at such high temperatures constitute a fire hazard and the glass envelope is subjected to the danger of erackin it hit by a sudden rain squall. It has even. een suggested to provide pyrex glass tubes for such signs.

It is the object of the present invention to provide a gaseous discharge tube which will have a bluish color'when in operation, and

the functioning ofwhich remains practically unaffected by tom erature changes in the surrounding atmosp ere.

In accordance with the present embodiment of the invention, I attaln-this object by providing external instead of internal electrodes. on the tube. As well known, such tubes provided with'external electrodes run cold. After exhaustion the tube is filled with a rare gas, preferably argon or helium, or a mixture ofboth, and a small quantity of mercury amalgam is introduced within the transparent envelope of the device. Various amalgams. may be used and I obtained good results with copper and sodium amalgams. The discharge tube is protected against impurities that may be evolved during its operation by means of an internal electrode in the form of a thin copper wire which'is connected with. one of the external electrodes in the manner described in my co-pepding applicain within said envelope and connected with tion Serial No. 147,298, filed November 9, 1926. The mercury amalgam may be obtained by rubbing some mercury on the internal copper electrode, which will amalgamate with the copper during the cleaning-up process, or it may be introduced in the form of an amalgam into the vessel itself.

A tube constructed in accordance with the present invention is illustrated in cross-section in the accompanying drawing in which 1 is the glass or other transparent or translucent tube, 2 and 3 the external electrodes, and 4 the internal or'clean-up electrode. 5 indicates the mercury amalgam.

I have found that tubes constructed in this manner will easily start, operate for several thousand hours without refilling, and maintain their characteristic bluish color at any temperature down to about 0 F. Below 0 F. the color of the tube turns to violet. The temperature of the glass envelope remains constantly substantially that of the surrounding atmosphere. If the envelope is of uranium glass,then during the operation of the tube, the blue colored gas appears within a green frame and presents a particularly pleasing effect.

What I claim is:

1. In a discharge tube, a translucent envelope filled with a rare gas, a sodium mercury amalgam in said envelope, two external electrodes and one internal electrode for said envelope, and a connection between said internal and one of said external electrodes.

2. In a discharge tube, a translucent envelope filled with helium, a mercury amalgam in said envelope, two external electrodes for said envelope, and a third electrode projecting within said envelope and connected with one of said external electrodes.

3. In a discharge tube, a glass envelope filled with helium, a sodium-mercury amalgain in said envelope, two external electrodes for said envelope, and a copper wire projecton? of said external electrodes.

In testimony whereof, I have signed my name to this specification this 7th day of December, 1926.

WILLIAM F. HENDRS/F. m 

